MIL-88A derived CoFe-layered double hydroxides with optimized composition for the enhanced electrocatalytic oxygen evolution reaction

Abstract

The oxygen evolution reaction (OER) as the anodic half-reaction of water electrolysis has received growing attention due to its paramount role in the green and sustainable production of hydrogen fuel and metal–air batteries. Herein, we report the synthesis of five CoFe-layered double hydroxides (CoFe-LDHs) and their application toward the electrocatalytic OER in an alkaline medium. CoFe-LDHs were prepared via a novel hydrothermal route from the MIL-88A metal–organic framework (MOF). The Co-to-Fe ratios in the LDHs were systematically modified to tune the electrocatalytic activity in the OER. It was observed that the as-prepared Co_0.39Fe_0.61-LDH demonstrated a superior electrocatalytic performance compared to the rest of the materials. More precisely, Co_0.39Fe_0.61-LDH required an overpotential of 227 mV to derive 20 mA cm⁻² current density with a Tafel slope of 36.8 mV dec⁻¹ and exhibited remarkable electrochemical stability. Besides, this LDH delivered an industrial-scale current density of 600 mA cm⁻² at an overpotential of 284 mV. Our results imply that modulating the metal content of LDHs is a simple yet effective strategy to promote their electrocatalytic activity toward the OER.